People may be learning while they're sleeping -- an unconscious form of memory that is still not well understood, according to a study by Michigan State University researchers.

"We speculate that we may be investigating a separate form of memory, distinct from traditional memory systems," said Kimberly Fenn, assistant professor of psychology and lead researcher on the project. "There is substantial evidence that during sleep, your brain is processing information without your awareness and this ability may contribute to memory in a waking state."

In the study of more than 250 people, Fenn and Zach Hambrick, associate professor of psychology, suggest people derive vastly different effects from this "sleep memory" ability, with some memories improving dramatically and others not at all. This ability is a new, previously undefined form of memory.

"This is the first step to investigate whether or not this potential new memory construct is related to outcomes such as classroom learning," Fenn said.